Providing of a guiding element for the airflow in the shape of a “spike” or so called “aerospike” is known since more than 50 years. Such elements are used for decreasing the pressure and/or the temperature at the front surface of a flying object which moves with supersonic velocities, see    Chang, P. K., “Separation of Flow”, Pergamon Press, 1970. [1]
Further prior art concerning the general object of reducing the wave drag at blunt flying objects as well as the use of aerospikes might be taken from the following literature:    Bertin J., “Hypersonic Aerothermodynamics”, AIAA Education Series, 1994 [2]    Formin V. M., Tretyakov P. K., Taran J.-P. “Flow Control Using Various Plasma And Aerodynamic Approaches (Short Review)”, Aerospace Science and Technology, 8, 2004, pages 411-421 [3]    Kremeyer K., “Lines of Pulsed Energy for Supersonic/Hypersonic Drag Reduction; Generation and Implementation”, AIAA-2004-0984, AIAA, 2004 (see also: Kremeyer, K., USPTO, U.S. Pat. No. 6,527,221 B1, May 2000 [4]    Gnemmi P., Srulijes J., Roussel K., Runne K., “Flowfield Around Spiked-Tipped Bodies for High Attack Angles at Mach 4.5”, Journal of Spacecraft and Rockets, Vol. 40, No. 5, pages 622-631, September-October 2003 [5]
One well known example for the use of an aerospike for a flying object is the missile intended for long distances named TRIDENT. For such missile the aerospike is mounted at a nose that might be semi-spherical or a head of the flying object including a device for seeking a target. The aerospike is aligned with the longitudinal axis of the flying object. During linear flight the aerospike leads to an induced flow separation at the distal end region of the aerospike. Such phenomenon is a result of an interaction of a bow shock wave with the boundary layer of the aerospike. The induced flow separation leads to a significant decrease of the wave drag which according to [1] sums up to 80%.
German Patent No. DE 199 53 701 C2, corresponding to U.S. Pat. No. 6,581,870, includes the observation that during flight conditions with the upstream airflow not exactly aligned with the longitudinal axis of the flying object the separated flow at the distal end of the aerospike is moved to a “lee side” whereas the upwind region of the front surface of the flying object is hit by the airflow. For such flight conditions despite the use of the aerospike, undesired increases of the temperature as well as the pressure may be observed. DE 199 53 701 C2 suggests using an aerospike with a spherical, ellipsoidal or drop-shaped extension instead of an aerospike with a constant cross-section with a tip or a plate-like element at its distal end. Such design leads to a shock wave at the distal end region of the aerospike which is immediately damped by an expansion fan. Downstream of the expansion a flow separation occurs at the lee side of the extension. The separated flow merges with the following separation bubble at the front of the hemispherical nose of the flying object. Accordingly, that leads to the reduction of the pressure at the entire front surface of the flying object resulting in a decrease of the wave drag as well as of the heat loads. Accordingly, an extension which might be spherical should lead to the airflow in the region of the front surface of the flying object being to the greatest possible extent independent on the angle between the airflow upstream the flying object and the longitudinal axis of the flying object.
U.S. Pat. No. 3,713,607 discloses an aerospike for a flying object moving with supersonic velocity wherein the aerospike comprises the shape of a hollow cylinder and the girthed area of the cylinder is perforated. The fixation of the aerospike at the front surface of the flying object is designed such that during manufacturing, mounting and prior to the start of the flying object it is possible to adjust the angle between the longitudinal axis of the aerospike and the longitudinal axis of the flying object according to expected flight conditions.
Further prior art is known from AIAA 95-0730, DE 36 12 175 C1, corresponding to U.S. Pat. No. 4,756,492, and U.S. Pat. No. 6,527,221 B1.